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Progress Toward a Bird Flu Vaccine

An experimental bird flu vaccine triggered a powerful immune response in more than half of the volunteers who received it. The approach might lead to better vaccines against a variety of flu viruses.

Influenza, or flu, claims thousands of lives nationwide each year. Some flu viruses that infect birds or other animals can change (or mutate) and become able to infect people. This is what happened in the case of the H7N9 bird flu virus. Human H7N9 infections were first reported last year in China. Most affected people had contact with infected poultry.

To test an experimental H7N9 vaccine, NIH-funded researchers enrolled 700 healthy adults in a clinical study. All received 2 injections of the vaccine at differing doses about 3 weeks apart. Some of the vaccines were combined with an adjuvant, a substance that promotes production of antibodiesGerm-fighting molecules made by the body’s immune system..

The researchers found that the best antibody responses occurred when the vaccine was coupled with the adjuvant. Among those who received 2 injections of the lowest vaccine dose with adjuvant, 59% had a powerful antibody response. Without the adjuvant, even the highest vaccine dose prompted little response.

The scientists also found evidence that just a single dose of the vaccine plus adjuvant may be enough to protect against the virus. Still, more research is needed to see how long the antibody responses may last.

“Although this influenza virus does not currently spread easily from person to person, all novel influenza viruses have the potential to evolve to cause widespread illness or death,” says Dr. Anthony S. Fauci, director of NIH’s National Institute of Allergy and Infectious Diseases. “It is prudent to conduct clinical trials such as this one to be prepared in the event of an H7N9 avian influenza pandemic.”